Fixing XML config example in docs.
Fixing XML config example in docs.

fcrepo4-archive/metrics,AltitudeDigital/metrics,kevintvh/metrics,unitsofmeasurement/metrics,dropwizard/metrics,slachiewicz/metrics,mnuessler/metrics,gburton1/metrics,jasw/metrics,rexren/metrics,gburton1/metrics,mtakaki/metrics,signalfx/metrics,mattnelson/metrics,ind9/metrics,dropwizard/metrics,tempredirect/metrics,egymgmbh/metrics,erikvanoosten/metrics-scala,ohr/metrics,fcrepo4-archive/metrics,gorzell/metrics,thelastpickle/metrics,gorzell/metrics,infusionsoft/yammer-metrics,dropwizard/metrics,Banno/metrics,chenxianghua2014/metrics,infusionsoft/yammer-metrics,gorzell/metrics,randomstatistic/metrics,mveitas/metrics,wfxiang08/metrics,bentatham/metrics,jplock/metrics,cirrus-dev/metrics,valery1707/dropwizard-metrics,timezra/metrics,mveitas/metrics,wickedshimmy/metrics-scala,mspiegel/metrics,maciej/metrics-scala,slovdahl/metrics,mt0803/metrics,scullxbones/metrics-scala,ChetnaChaudhari/metrics